For base station antennas in the mobile communications sector, phase-fixed interconnection of two or more radiator components to form radiator blocks has become common in certain embodiments. The effort and expense for the feed network can be reduced by means of combining radiators to form fixed blocks, thereby reducing costs, but also reducing the need for space, the production effort, and the mass of the antenna as a whole. The most frequent case is interconnection of two radiators to form a unit. While interconnection using suitable combiners and coaxial cables in the form of strip lines in air is fundamentally usual and continues to be usual in the case of frequency ranges below 1.0 GHz, in recent years implementation with circuit boards has proven itself as a good approach for broadband and cost-advantageous solutions, above all in the frequency range of 1.0 GHz to 4.0 GHz and beyond.
In order to supply one or more radiators with the desired electrical signals and to be able to implement suitable input impedances at defined interfaces by way of transformation structures, circuit boards using micro-strip technology have proven to be a good solution approach. Coaxial cables or other signal lines, which are an integral part of the supply network of the antenna, can be affixed at these interfaces.
The usual implementation of radiator blocks using strip lines (for example micro-strip) is that the interconnect structure of the circuit board is directed more or less in the direction of the main beam direction of the antenna, while the ground surface of the circuit board faces the reflector of the antenna, but is generally capacitively separated from it by means of an electrically insulating varnish, a film or another thin insulator. As a result of this open structure of the circuit board on the radiator side of the antenna, not only the desired properties but also possibilities for undesirable interactions of the circuit board with the radiators as well as the other surroundings, such as the reflector or other electrically conductive structures occur. These interactions can have negative effects, since certain antenna parameters are influenced in disruptive manner and compensation is hardly possible, or only possible within certain limits, with increased effort.
In order to avoid undesirable interactions of open circuit board structures or, in general, of open conductor structures, usually shields or shield housings are used in electrical technology. Shielding covers or shield housings in different embodiments are used against high-frequency incoming or outgoing radiation on or of circuit boards or open conductor structures. Undesirable influences between different components in a system, for example an antenna, can be avoided in this way.
The function of a shield housing is fulfilled when the greatest possible shield attenuation is achieved in the working ranges or frequency ranges of the circuit boards or of the (antenna) system to be shielded. Shield housings are widespread in electrical technology, in the most varied embodiments, and different approaches can also be found in antenna technology and filter technology.
It is the task of this invention to provide shielding for individual radiators or for a radiator block having at least two dipoles, using an open conductor structure, in which disruptive interactions between the conductor structure and the radiators as well as the rest of the antenna are avoided.
This task is accomplished, according to the invention, by means of the characteristics of the independent claims. Advantageous embodiments are the object of the dependent claims.